Local area networks, such as are used, for example, in computer communications, are well-known and described in, for example, U.S. Pat. No. 5,041,963, entitled, "Local Area Network with an Active Star Topology Comprising Ring Controllers Having Ring Monitor Logic Function," by Ebersole, et al., issued Aug. 20, 1991; U.S. Pat. No. 4,998,247, entitled "Active Star-Configured Local Area Network," by Irvine-Halliday, et al., issued Mar. 5, 1991; U.S. Pat. No. 4,982,400, entitled "Ring Bus Hub For a Star Local Area Network," by Ebersole, issued Jan. 1, 1991; U.S. Pat. No. 4,825,435, entitled "Multiport Repeater," by Amundsen, et al., issued Apr. 25, 1989; U.S. Pat. No. 4,872,158, entitled "Distributed Control Rapid Connection Circuit Switch," by Richards, issued Oct. 3, 1989; U.S. Pat. No. 4,787,082, entitled "Data Flow Control Arrangement For Local Area Network," by Delaney, et al., issued Nov. 22, 1988; and U.S. Pat. No. 4,674,085, entitled "Local Area Network," by Aranguren, et al., issued Jun. 16, 1987; all of the foregoing being herein incorporated by reference.
The stations or nodes of a local area network may be configured in a variety of different shapes, such as, for example, a ring or a star. In a star-configured or local area hub network, multiple discrete, remote stations are coupled through a central site or station, termed a hub station. The hub station must then follow a particular or predetermined signaling protocol to establish communications and to determine the order in which remote stations are permitted to transmit data over the network in the form of electrical signals. In one such signaling protocol, termed round robin, each of the remote stations is separately polled for transmissions. Likewise, in a round robin signaling protocol only one station may transmit electrical signal data at a time.
As disclosed and described in Proposed Demand Priority Preliminary Draft, submitted to IEEE 802.12 by Hewlett Packard, dated January 1994, herein incorporated by reference, a round robin protocol has been proposed to the IEEE to be employed in local area networks transmitting data at 100 megabits, termed 100 base VG. A round robin protocol provides advantages over other known network protocols, such as the protocol employed by IEEE standard 802.3, also known as CSMA/CD (Carrier Sense Multiple Access with Collision Detector), such as, for example, 10 base T, particularly for multimedia communications tasks that may be time sensitive. For such multimedia tasks or applications, it is desirable to prioritize or control the access provided remote stations to the media or communications network so that, in general, the more important communications tasks are completed earlier than the less important tasks.
For a local area hub network, it is also desirable to have the capability to increase the size of the network without substantially degrading signal transmission performance; that is, it is desirable for the network to be extendible. However, as local area hub networks increase in size, the hardware for communications between remote stations of the network becomes increasingly complex. For example, technological limitations on the manufacture of integrated circuit chips restrict the number of ports that may be fabricated on one chip. Thus, for a large local area hub network having tens or hundreds of stations, communications between remote stations directly linked or coupled to one hub station or one hub station network may need to be shared or allocated among several, discrete devices. The problem of transmitting electrical signals, typically digital signals, between the devices so that the electrical signals reach the intended remote station also becomes more complex. Thus, a need exists for a simple and reliable method of transmitting electrical signals in an extendible local area hub network.